It is a requirement of combined PET/MRI scanners to arrange the units required for recording the MRI and PET data within the MR magnet and the MR gradient coil. In this case, it is a requirement to design the RF sending/receiving system for MR signals, and the PET detector so that they are as small and as integrated as possible so that the opening of the PET/MRI scanner can be chosen to be as large as possible and the greatest amount of space is provided for the patient to be examined. The RF sending/receiving system is arranged around the patient opening in the proximity of the patient so that both the RF radiation can be radiated into the patient to excite the magnetic resonance, and the resulting magnetic resonance signals can be detected by the receiving system. In the region of the PET detector lying further outside, it is a requirement to design the RF sending/receiving system to be as permeable as possible to PET radiation. After its creation in the body of the patient, PET radiation is absorbed or scattered on its path to the PET detector when traversing solid matter and the tissue of the patient. These processes lead to an attenuation of the PET radiation, which adversely affects the capability of the system.
It is necessary to provide a surrounding radio-frequency screen around the RF sending/receiving system, so that as little radiation as possible is emitted by the sending/receiving system. The radio-frequency screen includes, for example, circuit boards which are laminated with copper on one side or on both sides, the copper layers having thicknesses in the range of 9 to 18 μm and being provided with slots to suppress turbulent gradient flows. The radio-frequency screen must in this case be fixed to a robust load-bearing structure, so that a defined relative position in relation to the RF antenna can be maintained and the generation of noise is avoided. In known solutions, the structure is generally composed of solid glass-reinforced plastic (GRP) or a comparable material. However, these are not optimum materials due to the excessively strong damping of the PET radiation.